102 research outputs found
Artesunate inhibits prostaglandin E2 (PGE2) production in LPS + IFN-γ activated BV-2 microglia cells
No full textThe impact of M&A on the Nigerian financial market: a pre-post analysis
No full textThis paper examines the impact of mergers and acquisitions (M&A) on the financial performance of the Nigerian market after consolidation. The authors use data from all Nigerian banks that survived the consolidation between 2001 and 2009. Logistic regression models are structured to determine the influence of M&A activities on the financial performance of the Nigerian market. Also, the authors critically evaluate the findings by shedding the light on the
lessons other developing nations can learn from the Nigerian market. The results show that M&A have a positive influence on the financial performance of the Nigerian market. Still, M&A are not enough to achieve the wider objectives of banking sector reform. Towards this end, corporate governance reform must take place vis-à-vis consolidation exercises especially when these M&A are regulatory based rather than market based. The investigation uses a novel approach by comparing pre- and post- M&A results performance of merged banks as well as comparing these results with non-merged banks. Finally, the paper puts the results in context of the wider reform context and considers the effectiveness of the M&A as a tool for banking sector reform in developing countries. The investigation offers insights into the policy of banking consolidation which can be useful for policy makers in Nigeria and other
similar economies
A survey on the use and impact of information technology in quantity surveying service delivery in Nigeria
No full textThe construction industry has recently witnessed a paradigm shift from traditional paper-based method of service delivery to electronic information exchange using Information Technolog (IT), at least in the western world like UK. It is now evident that the adoption of IT can enhance construction productivity and improve communications for effective decision-making and coordination among construction participants. The ability of the industry to avail itself of technology depends on the level of usage by construction participants including the Quantity Surveyor (QS) who plays a major role in the management of project success determinants, such as cost, time and quality. This research therefore evaluates the level of adoption of IT by QS in Nigeria and its impact in discharging their professional obligations to achieve improved service delivery. A review of the relevant literature using published sources was conducted to identify the current state and use of IT in the industry in various parts of the world. In order to assess the level of adoption of technology by QS in Nigeria and to evaluate its impact on their service delivery, data collected through questionnaires administered to practicing professionals were analysed and subsequently ranked using their mean item score (MIS) and the Kruskal Wallis H test. The research revealed that despite the average to high awareness of the importance of IT in improving service delivery and productivity, QS in Nigeria are still reluctant in using these technologies mainly due to the high initial cost of acquisition; lack of infrastructures to support its use and security concerns such as the susceptibility of IT system. It is concluded that the Nigerian Institute of Quantity Surveyors should act as a champion in raising the awareness of IT among its members and the Government should provide an enabling environment for its importation and usage
White Blood Cell and Serum Biochemistry of Rabbits on Varying Levels of Oyster Mushroom (Pleurotus Ostreatus) Extract under Two Housing Types
No full textA total of ninety-six, six weeks old rabbits were grouped into two housing types (steel and wooden hutches), sex (male and female) and four inclusion levels (0 , 5, 10 and 15 ml) of oyster mushroom extract per litre of water in a 2 × 2 × 4 factorial experimental layout. One rabbit each was selected from each replicate at end of the 10th week of the experiment for white blood cell and serum biochemistry analysis. Results showed that growing rabbits on 5 ml of mushroom (Pleurotus ostreatus) extract per litre of drinking water had the lowest (P < 0.05) neutrophil (31.00 %) and the highest (P < 0.05) lymphocyte (67.25 %) in the white blood cell. Male rabbits in steel hutch have a higher (P < 0.05) eosinophil (0.75 %) in the white blood cell than the female rabbits in steel hutch (0.00 %). Rabbits in steel hutch had a lower (P < 0.05) low density lipoproteins (13.89 mg/dl) in the serum than rabbits housed in wooden hutch (16.02 mg/dl). It was concluded that housing rabbits in wooden hutch and inclusion of oyster mushroom up to 15 ml as phytobiotic for rabbits would optimize their health status
Managing workplace violence in an outpatient mental health clinic
No full textWorkplace violence (WPV) is a complex and hazardous occupational problem healthcare workers face daily. The prevalence of WPV has increased exponentially in the healthcare industry in the past decade, specifically in outpatient mental health clinics. The increase is attributed to limited access to quality mental healthcare, poverty, substance abuse, and hereditary factors predisposing many individuals to mental health disorders. The purpose of this project is to determine the effect of WPV prevention training program and the use of violence risk assessment tools on the occurrence of patient-on-provider violence in outpatient mental health settings. Methodology: This project used a quasi-experimental design as the most suitable approach to assess the implementation of a violence risk assessment tool and WPV prevention training that targets incident of patient aggression. Results: Project results showed an increase in violence risk assessment post-implementation evidenced by a 53% increase in V-RISK-10 utilization. Also, there was a 36.4% decrease in patient-on-provider violent cases. Implications for practice: The result indicates an improved employees' workplace safety and violence prevention competency. It also provides a cost-effective way to manage type II violence.D.N.P.Includes bibliographical reference
Concentrado restringido con la alimentación de forraje ad libitum: efectos sobre el comportamiento y rendimiento de la canal de conejos en crecimiento
No full textEffect of concentrate feed restriction in the presence of ad libitum
forage feeding on performance, carcass yield and relative organ weights
were investigated in weaner rabbits in a humid tropical environment in
Nigeria. Thirty six growing rabbits of mixed breed (Chinchilla x Dutch
x California White) and sexes with an average weight of 600g were
assigned to three feeding regimen in a completely randomized design.
The study lasted for 8 weeks. The three feeding regimen were: (A) ad
libitum concentrate feeding + ad libitum forage feeding (control), (B)
skip-a-day concentrate feeding/week + ad libitum forage feeding and (C)
skip-2-days concentrate feeding/week + ad libitum forage feeding. The
forage used was air-dried Tridax procumbens. Drinking water was
supplied free-choice throughout the duration of the experiment. Each
treatment group was replicated six times with two rabbits
housed/replicate. Weight gain, final body weight, feed intake and feed:
gain ratio of rabbits were not significantly (P>0.05) different
among the treatment groups. Although feed intake was not different
among the three treatments, however concentrate intake, forage intake
as well as percentage concentrate and forage in daily feed intake were
significantly (P<0.05) influenced by treatments. Total concentrate
intake was significantly higher in rabbits on treatment A (ad libitum
feeding) compared with rabbits on treatment B which was also
significantly higher than the intake on treatment C. Rabbits fed ad
libitum consumed 10.75 and 25.94% more concentrates than rabbits on
skip-a-day and skip-two-days per week concentrate feeding. Daily
concentrate intake reduced from 33.35g on treatment A to 29.76g and
24.69g in treatment B and C respectively. The daily forage intake
however increased with severity of concentrate restriction, the trend
being C > B > A. The concentrate percentage of daily feed intake
reduced with increased severity of concentrate restriction while that
of forage increased with concentrate restriction from 56.15% in ad
libitum concentrate fed group to the highest amount of 68.45% in
rabbits on skip-two-days of concentrate feeding per week. Dressing
percentage and retail cuts were not significantly (P > 0.05)
affected by feeding regime. Similarly the physical structure and
weights of internal organs (livers, kidneys, lungs and hearts) were not
affected by experimental treatments (P>0.05). The results obtained
from this study showed that rabbits can be subjected to two days
skipping of concentrate feed per week with ad libitum forage feeding
without compromising performance and carcass measurements.Se investigaron los efectos de la restricción de alimento
concentrado en la presencia de la alimentación de forraje ad
libitum sobre el comportamiento, el rendimiento en canal y pesos
relativos de órganos en conejos destetados en un ambiente
húmedo tropical en Nigeria. Treinta y seis conejos en crecimiento
de raza mezclada (Chinchilla x Dutch x California White) y sexos con un
peso promedio de 600 g se asignaron a tres regímenes de
alimentación en un diseño completamente aleatorizado. El
estudio se prolongó durante 8 semanas. Los tres regímenes de
alimentación fueron: (A) alimentación con concentrado ad
libitum + alimentación con forraje ad libitum (control), (B)
alimentación con concentrado cada dos días por semana +
alimentación con forraje ad libitum y (C) alimentación con
concentrado cada tres días por semana + alimentación con
forraje ad libitum. El forraje utilizado fue de Tridax procumbens
secado al aire. El agua potable se suministró de libre
elección durante toda la duración del experimento. Cada grupo
de tratamiento se repitió seis veces con dos conejos
alojados/repetición. La ganancia de peso, el peso corporal final,
consumo de alimento y la relación consumo:ganancia de los conejos
no fueron significativamente (P>0,05) diferentes entre los grupos de
tratamiento. Aunque el consumo de alimento no fue diferente entre los
tres tratamientos, sin embargo, el consumo de concentrado, el consumo
de forraje, así como el porcentaje de concentrado y forraje en el
consumo diario de alimento fueron significativamente (P<0,05)
influenciados por los tratamientos. El consumo total de concentrado fue
significativamente mayor en los conejos del tratamiento A
(alimentación ad libitum) comparado con los conejos en el
tratamiento B, el cual también fue significativamente mayor que la
ingesta del tratamiento C. Los conejos alimentados ad libitum
consumieron 10,75 y 25,94% más concentrado que aquellos conejos
con alimentación con concentrado cada dos y tres días por
semana. El consumo diario de concentrado se redujo de 33,35 g en el
tratamiento A a 29,76 y 24,69 g en el tratamiento B y C,
respectivamente. El consumo diario de forraje, sin embargo,
aumentó con la severidad de la restricción de concentrado, la
tendencia fue C > B > A. El porcentaje de concentrado del consumo
diario de alimento se redujo con incrementos de la severidad de la
restricción de concentrado, mientras que aquel del forraje se
incrementó con la restricción de concentrado de 56,15% en el
grupo alimentado con concentrado ad libitum hasta la mayor cantidad de
68,45% en los conejos alimentados con concentrado cada dos días
por semana. El rendimiento en canal y los cortes al por menor no fueron
significativamente (P>0,05) afectados por el régimen de
alimentación. Similarmente, la estructura física y el peso de
los órganos internos (hígado, riñones, pulmones y
corazón) no fueron afectados por los tratamientos experimentales
(p>0,05). Los resultados obtenidos de este estudio mostraron que los
conejos pueden ser sujetos a una alimentación de concentrado cada
dos días por semana con foraje ad libitum sin comprometer el
rendimiento y las medidas de la canal
Concentrado restringido con la alimentación de forraje ad libitum: efectos sobre el comportamiento y rendimiento de la canal de conejos en crecimiento
No full textEffect of concentrate feed restriction in the presence of ad libitum
forage feeding on performance, carcass yield and relative organ weights
were investigated in weaner rabbits in a humid tropical environment in
Nigeria. Thirty six growing rabbits of mixed breed (Chinchilla x Dutch
x California White) and sexes with an average weight of 600g were
assigned to three feeding regimen in a completely randomized design.
The study lasted for 8 weeks. The three feeding regimen were: (A) ad
libitum concentrate feeding + ad libitum forage feeding (control), (B)
skip-a-day concentrate feeding/week + ad libitum forage feeding and (C)
skip-2-days concentrate feeding/week + ad libitum forage feeding. The
forage used was air-dried Tridax procumbens. Drinking water was
supplied free-choice throughout the duration of the experiment. Each
treatment group was replicated six times with two rabbits
housed/replicate. Weight gain, final body weight, feed intake and feed:
gain ratio of rabbits were not significantly (P>0.05) different
among the treatment groups. Although feed intake was not different
among the three treatments, however concentrate intake, forage intake
as well as percentage concentrate and forage in daily feed intake were
significantly (P<0.05) influenced by treatments. Total concentrate
intake was significantly higher in rabbits on treatment A (ad libitum
feeding) compared with rabbits on treatment B which was also
significantly higher than the intake on treatment C. Rabbits fed ad
libitum consumed 10.75 and 25.94% more concentrates than rabbits on
skip-a-day and skip-two-days per week concentrate feeding. Daily
concentrate intake reduced from 33.35g on treatment A to 29.76g and
24.69g in treatment B and C respectively. The daily forage intake
however increased with severity of concentrate restriction, the trend
being C > B > A. The concentrate percentage of daily feed intake
reduced with increased severity of concentrate restriction while that
of forage increased with concentrate restriction from 56.15% in ad
libitum concentrate fed group to the highest amount of 68.45% in
rabbits on skip-two-days of concentrate feeding per week. Dressing
percentage and retail cuts were not significantly (P > 0.05)
affected by feeding regime. Similarly the physical structure and
weights of internal organs (livers, kidneys, lungs and hearts) were not
affected by experimental treatments (P>0.05). The results obtained
from this study showed that rabbits can be subjected to two days
skipping of concentrate feed per week with ad libitum forage feeding
without compromising performance and carcass measurements.Se investigaron los efectos de la restricción de alimento
concentrado en la presencia de la alimentación de forraje ad
libitum sobre el comportamiento, el rendimiento en canal y pesos
relativos de órganos en conejos destetados en un ambiente
húmedo tropical en Nigeria. Treinta y seis conejos en crecimiento
de raza mezclada (Chinchilla x Dutch x California White) y sexos con un
peso promedio de 600 g se asignaron a tres regímenes de
alimentación en un diseño completamente aleatorizado. El
estudio se prolongó durante 8 semanas. Los tres regímenes de
alimentación fueron: (A) alimentación con concentrado ad
libitum + alimentación con forraje ad libitum (control), (B)
alimentación con concentrado cada dos días por semana +
alimentación con forraje ad libitum y (C) alimentación con
concentrado cada tres días por semana + alimentación con
forraje ad libitum. El forraje utilizado fue de Tridax procumbens
secado al aire. El agua potable se suministró de libre
elección durante toda la duración del experimento. Cada grupo
de tratamiento se repitió seis veces con dos conejos
alojados/repetición. La ganancia de peso, el peso corporal final,
consumo de alimento y la relación consumo:ganancia de los conejos
no fueron significativamente (P>0,05) diferentes entre los grupos de
tratamiento. Aunque el consumo de alimento no fue diferente entre los
tres tratamientos, sin embargo, el consumo de concentrado, el consumo
de forraje, así como el porcentaje de concentrado y forraje en el
consumo diario de alimento fueron significativamente (P<0,05)
influenciados por los tratamientos. El consumo total de concentrado fue
significativamente mayor en los conejos del tratamiento A
(alimentación ad libitum) comparado con los conejos en el
tratamiento B, el cual también fue significativamente mayor que la
ingesta del tratamiento C. Los conejos alimentados ad libitum
consumieron 10,75 y 25,94% más concentrado que aquellos conejos
con alimentación con concentrado cada dos y tres días por
semana. El consumo diario de concentrado se redujo de 33,35 g en el
tratamiento A a 29,76 y 24,69 g en el tratamiento B y C,
respectivamente. El consumo diario de forraje, sin embargo,
aumentó con la severidad de la restricción de concentrado, la
tendencia fue C > B > A. El porcentaje de concentrado del consumo
diario de alimento se redujo con incrementos de la severidad de la
restricción de concentrado, mientras que aquel del forraje se
incrementó con la restricción de concentrado de 56,15% en el
grupo alimentado con concentrado ad libitum hasta la mayor cantidad de
68,45% en los conejos alimentados con concentrado cada dos días
por semana. El rendimiento en canal y los cortes al por menor no fueron
significativamente (P>0,05) afectados por el régimen de
alimentación. Similarmente, la estructura física y el peso de
los órganos internos (hígado, riñones, pulmones y
corazón) no fueron afectados por los tratamientos experimentales
(p>0,05). Los resultados obtenidos de este estudio mostraron que los
conejos pueden ser sujetos a una alimentación de concentrado cada
dos días por semana con foraje ad libitum sin comprometer el
rendimiento y las medidas de la canal
Soybean meal replacement with cassava leaf:Blood meal mix with or without enzyme in broiler diets
No full textTwo hundred and sixteen unsexed day-old
Cobb broilers of a commercial strain were used to
study the effect of replacement of soybean meal
(SBM) by cassava leaf:blood meal mix (CLM:BM)
with or without enzyme supplementation on broiler
growth and performance. The birds were divided
into 6 groups of 36 birds each after balancing for
live weight. Each group was further sub-divided
into 6 replicates of 6 birds each. CLM:BM replaced
SBM at 0, 25 and 50 % on weight for weight basis.
The resulting three dietary combinations were
supplemented with a commercial enzyme
(Maxigrain ® ) at the rates of 0 and 100 ppm thus
resulting in 6 dietary treatments. The six groups of
36 birds were randomly allotted to the six experi-
mental diets. Feed and water were provided free
choice during the 56 days experimental period
during which data were collected on performan-
ce, nutrient retention, feed transit time and carcass
characteristics of birds. Replacement of SBM with
CLM:BM mix had no effect (p>0.05) on weight gain
(WG), feed intake (FI), feed: gain ratio (F:G), crude
protein (CP), ether extract (EE) and crude fibre
retention (CF), dressing percentage, breast cut,
drumstick, thigh liver and kidney weights but
significantly (p<0.05) reduced intestinal transit
time (ITT) and abdominal fat while increasing
gizzard and caecum weight. Enzyme supple-
mentation however significantly (p<0.05) improve
WG and reduced F:G, improved (p>0.05) nutrient
retention, dressing and abdominal fat percentage
but had no effect on FI. No mortality was recorded
in the course of this study. Enzyme supplementation
significantly (p<0.05) reduced gizzard and caecum
weights. It was concluded that in broiler feeding
CLM:BM mix can effectively replace 50 % SBM
without adverse effect on the birds. Supplemen-
tation of diets with enzyme led to further impro-
vement in performance of broilers.Doscientos dieciseis pollos Cobb, de un día, no
sexados, fueron empleados para estudiar el efec-
to de la sustitución de la harina de soja (SBM) por
una mezcla de hojas de yuca:harina de sangre
(CLM:BM), con o sin adicción de enzimas, sobre
el crecimiento y productividad de los broilers. Se
formaron 6 grupos de 36 aves cada uno después
de equilibrarlas en función del peso vivo. Cada
grupo fue después subdividido en 6 repeticiones
de 6 aves cada una. La mezcla CLM:BM se empleó
para sustituir a la SBM en proporciones de 0, 25
y 50 % (peso/peso). Las tres combinaciones
dietarias resultantes fueron suplementadas con
un enzima comercial (Maxigrain ® ) en proporciones
de 0 y 100 ppm resultando así 6 tratamientos
dietéticos. Los seis grupos de 36 aves fueron
aleatoriamente asignados a las seis dietas expe-
rimentales. El pienso y el agua fueron suministra-
dos a voluntad durante los 56 días de periodo
experimental durante el cual se obtuvieron los
datos relativos a productividad, retención de
nutrientes, tiempo de tránsito del pienso y carac-
erísticas de la canal de las aves. La sustitución de
SBM por la mezcla CLM:BM no tuvo efecto (p>0,05)
sobre la ganancia de peso (WG), ingestion de
pienso (FI), tasa de pienso:ganancia de peso,
retención de proteína bruta (CP), extracto etéreo
(EE) y fibra bruta (CF), rendimiento a la canal,
pesos de pechuga, patas, muslos, higado y riño-
nes. Sin embargo, mejoró significativamente
(p<0,05) WG y redujo la relación F:G (p<0,05);
mejoró (p<0,05) la retención de nutrientes, el
rendimiento y porcentaje de grasa abdominal sin
afectar a FI. No se registró mortalidad a lo largo del
experimento. La suplementación enzimática redu-
jo significativamente (p<0,05) el peso de molleja y
ciego. Se concluyó que en la alimentación de
broilers la mezcla CLM:BM puede sustituir eficaz-
mente al 50 % de la harina de soja sin producir
efectos adversos. La adicción de enzimas a las
dietas no produjo mejoras adicionales de la pro-
ductividad de los pollo
Restricted concentrate with ad libitum forage feeding: effects on performance and carcass yield of growing rabbits
No full textEffect of concentrate feed restriction in the presence of ad libitum forage feeding on performance, carcass yield and relative
organ weights were investigated in weaner rabbits in a humid tropical environment in Nigeria. Thirty six growing rabbits of
mixed breed (Chinchilla x Dutch x California White) and sexes with an average weight of 600g were assigned to three
feeding regimen in a completely randomized design. The study lasted for 8 weeks. The three feeding regimen were: (A) ad
libitum concentrate feeding + ad libitum forage feeding (control), (B) skip-a-day concentrate feeding/week + ad libitum
forage feeding and (C) skip-2-days concentrate feeding/week + ad libitum forage feeding. The forage used was air-dried
Tridax procumbens. Drinking water was supplied free-choice throughout the duration of the experiment. Each treatment
group was replicated six times with two rabbits housed/replicate. Weight gain, final body weight, feed intake and feed: gain
ratio of rabbits were not significantly (P>0.05) different among the treatment groups. Although feed intake was not different
among the three treatments, however concentrate intake, forage intake as well as percentage concentrate and forage in daily
feed intake were significantly (P<0.05) influenced by treatments. Total concentrate intake was significantly higher in rabbits
on treatment A (ad libitum feeding) compared with rabbits on treatment B which was also significantly higher than the
intake on treatment C. Rabbits fed ad libitum consumed 10.75 and 25.94% more concentrates than rabbits on skip-a-day and
skip-two-days per week concentrate feeding. Daily concentrate intake reduced from 33.35g on treatment A to 29.76g and
24.69g in treatment B and C respectively. The daily forage intake however increased with severity of concentrate
restriction, the trend being C > B > A. The concentrate percentage of daily feed intake reduced with increased severity of
concentrate restriction while that of forage increased with concentrate restriction from 56.15% in ad libitum concentrate fed
group to the highest amount of 68.45% in rabbits on skip-two-days of concentrate feeding per week. Dressing percentage
and retail cuts were not significantly (P > 0.05) affected by feeding regime. Similarly the physical structure and weights of
internal organs (livers, kidneys, lungs and hearts) were not affected by experimental treatments (P>0.05). The results
obtained from this study showed that rabbits can be subjected to two days skipping of concentrate feed per week with ad
libitum forage feeding without compromising performance and carcass measurements.Se investigaron los efectos de la restricción de alimento concentrado en la presencia de la alimentación de forraje ad libitum
sobre el comportamiento, el rendimiento en canal y pesos relativos de órganos en conejos destetados en un ambiente
húmedo tropical en Nigeria. Treinta y seis conejos en crecimiento de raza mezclada (Chinchilla x Dutch x California White)
y sexos con un peso promedio de 600 g se asignaron a tres regímenes de alimentación en un diseño completamente
aleatorizado. El estudio se prolongó durante 8 semanas. Los tres regímenes de alimentación fueron: (A) alimentación con
concentrado ad libitum + alimentación con forraje ad libitum (control), (B) alimentación con concentrado cada dos días por
semana + alimentación con forraje ad libitum y (C) alimentación con concentrado cada tres días por semana + alimentación
con forraje ad libitum. El forraje utilizado fue de Tridax procumbens secado al aire. El agua potable se suministró de libre
elección durante toda la duración del experimento. Cada grupo de tratamiento se repitió seis veces con dos conejos
alojados/repetición. La ganancia de peso, el peso corporal final, consumo de alimento y la relación consumo:ganancia de los
conejos no fueron significativamente (P>0,05) diferentes entre los grupos de tratamiento. Aunque el consumo de alimento
no fue diferente entre los tres tratamientos, sin embargo, el consumo de concentrado, el consumo de forraje, así como el
porcentaje de concentrado y forraje en el consumo diario de alimento fueron significativamente (P<0,05) influenciados por
los tratamientos. El consumo total de concentrado fue significativamente mayor en los conejos del tratamiento A (alimentación ad libitum) comparado con los conejos en el tratamiento B, el cual también fue significativamente mayor que
la ingesta del tratamiento C. Los conejos alimentados ad libitum consumieron 10,75 y 25,94% más concentrado que
aquellos conejos con alimentación con concentrado cada dos y tres días por semana. El consumo diario de concentrado se
redujo de 33,35 g en el tratamiento A a 29,76 y 24,69 g en el tratamiento B y C, respectivamente. El consumo diario de
forraje, sin embargo, aumentó con la severidad de la restricción de concentrado, la tendencia fue C > B > A. El porcentaje
de concentrado del consumo diario de alimento se redujo con incrementos de la severidad de la restricción de concentrado,
mientras que aquel del forraje se incrementó con la restricción de concentrado de 56,15% en el grupo alimentado con
concentrado ad libitum hasta la mayor cantidad de 68,45% en los conejos alimentados con concentrado cada dos días por
semana. El rendimiento en canal y los cortes al por menor no fueron significativamente (P>0,05) afectados por el régimen
de alimentación. Similarmente, la estructura física y el peso de los órganos internos (hígado, riñones, pulmones y corazón)
no fueron afectados por los tratamientos experimentales (p>0,05). Los resultados obtenidos de este estudio mostraron que
los conejos pueden ser sujetos a una alimentación de concentrado cada dos días por semana con foraje ad libitum sin
comprometer el rendimiento y las medidas de la canal
Experimental Fluid-Structure Interaction: On Providing Reliable Experimental Data for Validation of Fluid Structure Interaction in ComFlow
No full textStructures at sea, which can either be floating or bottom-founded, are always affected by several types of dynamic loads from wind, waves and currents; with floating offshore structures subjected to more motion and loading from these loads. Hence, necessitating more in-depth hydrodynamic analyses. Increasing size and weight of these floating structures together with industry demands have led to unsuitability of existing models – which make use of rigid body (no hydroelasticity) assumptions. This, in addition to other reservations about current practices, has led to the need for more realistic formulations of the interaction between fluids and our offshore structures, taking hydroelasticity into account. Extreme wave impacts, which are responsible for severe damage of offshore structures, have for a long period been only studied with experimental methods, as non-linear nature of the complex wave kinematics make solutions not straightforward. More recent advancements have seen the development of numerical techniques and programs, based on the Navier-Stokes equations, to better understand extreme waves and impacts on offshore structures.This thesis focuses on the topic of experimental validation of fluid-structure interaction (FSI) in ComMotion – an advancement in the ComFLOW program (an improved Volume of Fluid (iVOF) Computational Fluid Dynamics (CFD) code) to capture motion of flexible structures in the presence of free surface effects and a two-way coupling between the fluid and the structure. This has led to the need to provide reliable data for validation purposes. The research is conducted in continuation of the studies carried out by Rizos (2016) in which an electromagnetic drive linear motor produced noise and variable amplitude enforcement obtained in the analyzed results, amidst other uncertainties in the measurement techniques used. The current methodology principally makes use of a different motion technique – rotary to linear motion to obtain more reliable data.Firstly, rotary to linear motion was chosen (motivated from the internal combustion engine of an automobile) and then verified computationally with analytical derivations. The experiments were then designed, with the initial step being to verify the said linear motion. A sensitivity of the motion signal to weights in the system was carried out. Further, the experiment designed made use of a latex rubber membrane, applied with a clamped boundary condition at the bottom of a partially-filled rigid cylindrical structure. Tension existing in the membrane, due to water columns above it, was analytically obtained, as complete knowledge of system parameters was crucial. Linear oscillatory motion at the end of the converted rotary motion was applied to the fluid-structure system. Motion signals were obtained – rigid body measurements, to subtract them from the membrane motion measurements obtained. Motion measurements were acquired with laser triangulation displacement devices and a force transducer was used to monitor applied forces in the plunger during the experiments. The output of the transducer can offer validation data to the FSI solver.Membrane measurements were taken at half radius at a 30° step over a 180° span, and at the centre. This was in a bid to capture maximum deflections of the membrane, as interest was to obtain the coupled frequency mode shape. Finally, the obtained membrane motion data were analysed to prove their reliability, and to draw conclusions from them. Volume (of liquid), frequency and polar dependence analyses were carried out. Recommendations were subsequently outlined, for future research.Offshore and Dredging EngineeringMarine Technology | Ship Hydromechanic
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